This invention relates generally to methods for durably binding a functional layer to a substrate surface, and more specifically to methods for durably binding a solid film lubrication layer to a substrate surface.
Friction is the resistance of one solid sliding over another solid. Often, the higher the friction the greater the wear. The best way to reduce friction and wear is by separating the surfaces. This can be accomplished by use of a liquid lubricant such as oil. The ideal condition is known as hydrodynamic lubrication and can eliminate wear by fully separating materials by a fluid film. Unfortunately, ideal conditions of hydrodynamic lubrication are rarely maintained in practice. Starting, stopping, misalignment, heavy loads and other conditions can cause a fluid film to be squeezed out, or allow surface asperities to break through the lubricant film, so that the two solids are pressed into contact with one another, ending that ideal hydrodynamic lubrication and beginning elastohydrodynamic or boundary lubrication. If no liquid is present, the surface is either self-lubricated (no lubrication) or a solid lubricant can be used. Solid film lubrication is a critical enabling technology employed in the absence of liquid lubricants. The choice to forgo a liquid lubricant or grease can be from either design constraints or too severe operating conditions for liquid and grease survival. Extreme operating conditions are typically defined by severe environments, such as from water, chemicals, temperatures and pressures. Extreme operating conditions require a distinct and separate class of lubricants. The harsh environment of outer space and internal combustion engines, for example, is marked by such extreme conditions and has spurred development of a special class of non-organic based lubricants. Solid film lubricants have been very successful in fulfilling the role of providing wear protection in such conditions. Relative to liquid lubricants, solid lubricants generally have lower vapor pressures, better boundary lubrication properties and relative insensitivity to radiation effects and operate in wider temperature ranges.